Greenland ice velocities: Envisat vs Radarsat-1 background missions

Eric Rignot(1)

(1) Jet Propulsion Laboratory, Ms 300-319, Pasadena CA 91109-8099, United States


In 2000, Radarsat-1 imaged the Greenland ice sheet during the background mission for the second Antarctic Mapping Mission AMM-2. We processed these data using a speckle tracking technique to produce a map of ice velocities along nearly the entire coast of the Greenland ice sheet. The method yields high precision velocities (10 m/yr), with high spatial sampling (50 m), over the ablation area of the ice sheet and in some cases over its accumulation area, for instance in the north and in central west Greenland. These data have been used to derive a new estimate of the mass balance of the ice sheet. Here, we use Envisat ASAR data acquired during Envisate background mission to measure ice velocity. Envisat is operated at VV-polarization, which is not as favorable for ice studies as HH-polarization (e.g. Radarsat-1) due to lower penetration in snow/ice, but its 35-day repeat cycles yields high precision velocity where speckle remains coherent. In this talk, we will compare Envisat and Radarsat-1 results over the same regions. One objective is to combine the observations to detect glacier acceleration in Greenland. In several sectors, we observe major speed up, for instance in southeast Greenland, on Helheim glacier, Jakobshavn Isbrae and several ice streams north of Jakobshavn. We will also report on the results of applying speckle tracking on wide swath data acquired in the polar regions.

This work was performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryospheric Sciences Program.


Workshop presentation


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